Long-standing hypotheses concerning the development and likely evolutionary origin of several classes of vertebrate dermal bone remain untested. Do scales and post-cranial dermal bones of extant fishes share a common evolutionary origin with teeth and fin rays? Do the osteogenic cells that produce scales and plates originate in the trunk neural crest, a tissue widely considered to lack osteogenic potential? What are the inducing tissues and signals that generate the pattern of squamation? I propose to address these questions with an analysis of molecular genetic mechanisms that initiate and pattern the post-cranial bony dermal plates of armored Gasterosteiform fish, the threespine stickleback and gulf pipefish, and with experimental embryological approaches to identify the origins of cells and signals involved in the development of these plates. This analysis will contribute to the field of fish integument development for which little information is currently available. In addition, these experiments are likely to meaningfully inform the study of human craniofacial and bone development, as Gasterosteiform bony plates share structural and developmental similarity with cranial dermal bones. [unreadable] [unreadable] [unreadable]